Structure and vibrational dynamics of interfacial Sn layers in SnÕSi multilayers
نویسندگان
چکیده
The structure and vibrational dynamics of room-temperature-grown nanoscale Sn/amorphous (a-!Si multilayers have been studied by x-ray diffraction, Raman scattering, Sn Mössbauer spectroscopy, and Sn nuclear-resonant inelastic x-ray scattering ~NRIXS! of synchrotron radiation. With increasing Sn-layer thickness, the formation of b-Sn was observed, except at the Sn/Si interfaces, where a 10-Å-thick metastable pure amorphous-a-Sn-like layer remains stabilized. By means of NRIXS we have measured the Sn-projected vibrational density of states ~VDOS! in these multilayers ~in particular, at the interfaces!, and in 500-Å-thick epitaxial a-Sn films on InSb~001! as a reference. Further, the Sn-specific Lamb-Mössbauer factor ( f factor!, mean kinetic energy per atom, mean atomic force constant, and vibrational entropy per atom were obtained. The VDOS of the amorphous-a-Sn-like interface layer is observed to be distinctly different from that of ~bulk! a-Sn and b-Sn, and its prominent vibrational energies are found to scale with those of amorphous Ge and Si. The observed small difference in vibrational entropy (DS/kB510.1760.05 per atom! between a-Sn and interfacial amorphous-a-like Sn does not account for the stability of the latter phase.
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